#include "cuda_runtime.h"
#include <cstdio>
#include <cstring>

// Global error state
static cudaError_t g_lastError = cudaSuccess;

// Error strings
static const char* errorStrings[] = {
    "cudaSuccess",
    "cudaErrorInvalidValue",
    "cudaErrorMemoryAllocation",
    "cudaErrorInitializationError",
    // ... add more as needed
    "cudaErrorUnknown"
};

#ifdef __cplusplus
extern "C" {
#endif

/**
 * @brief Memory management functions
 */

cudaError_t cudaMalloc(void** devPtr, size_t size) {
    // TODO: Implement device memory allocation
    (void)devPtr;
    (void)size;
    return cudaSuccess;
}

cudaError_t cudaFree(void* devPtr) {
    // TODO: Implement device memory deallocation
    (void)devPtr;
    return cudaSuccess;
}

cudaError_t cudaMemcpy(void* dst, const void* src, size_t count, enum cudaMemcpyKind kind) {
    // TODO: Implement memory copy between host and device
    (void)dst;
    (void)src;
    (void)count;
    (void)kind;
    return cudaSuccess;
}

cudaError_t cudaMemset(void* devPtr, int value, size_t count) {
    // TODO: Implement device memory set
    (void)devPtr;
    (void)value;
    (void)count;
    return cudaSuccess;
}

/**
 * @brief Device management functions
 */

cudaError_t cudaDeviceSynchronize(void) {
    // TODO: Implement device synchronization
    return cudaSuccess;
}

cudaError_t cudaDeviceReset(void) {
    // TODO: Implement device reset
    return cudaSuccess;
}

cudaError_t cudaGetDeviceCount(int* count) {
    // TODO: Implement get device count
    if (count) {
        *count = 1; // Simulate 1 device
    }
    return cudaSuccess;
}

cudaError_t cudaSetDevice(int device) {
    // TODO: Implement set device
    (void)device;
    return cudaSuccess;
}

cudaError_t cudaGetDevice(int* device) {
    // TODO: Implement get device
    if (device) {
        *device = 0; // Simulate device 0
    }
    return cudaSuccess;
}

/**
 * @brief Error handling functions
 */

const char* cudaGetErrorString(cudaError_t error) {
    // TODO: Implement proper error string lookup
    if (error == cudaSuccess) {
        return errorStrings[0];
    }
    return "Unknown error";
}

cudaError_t cudaGetLastError(void) {
    cudaError_t error = g_lastError;
    g_lastError = cudaSuccess;
    return error;
}

cudaError_t cudaPeekAtLastError(void) {
    return g_lastError;
}

/**
 * @brief Kernel launch functions
 */

cudaError_t cudaLaunchKernel(const void* func, dim3 gridDim, dim3 blockDim,
                             void** args, size_t sharedMem, cudaStream_t stream) {
    // TODO: Implement kernel launch via PTX VM
    (void)func;
    (void)gridDim;
    (void)blockDim;
    (void)args;
    (void)sharedMem;
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaConfigureCall(dim3 gridDim, dim3 blockDim, size_t sharedMem, cudaStream_t stream) {
    // TODO: Implement configure call for <<<>>> syntax
    (void)gridDim;
    (void)blockDim;
    (void)sharedMem;
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaSetupArgument(const void* arg, size_t size, size_t offset) {
    // TODO: Implement setup kernel argument
    (void)arg;
    (void)size;
    (void)offset;
    return cudaSuccess;
}

cudaError_t cudaLaunch(const void* func) {
    // TODO: Implement kernel launch after configuration
    (void)func;
    return cudaSuccess;
}

/**
 * @brief Registration functions (called by CUDA compiler-generated code)
 */

void** __cudaRegisterFatBinary(void* fatCubin) {
    // TODO: Implement fat binary registration and PTX extraction
    // This function should:
    // 1. Parse the .nv_fatbin section
    // 2. Extract PTX code
    // 3. Store PTX for later kernel launch
    (void)fatCubin;
    
    // Return a dummy handle for now
    static void* handle = nullptr;
    return &handle;
}

void __cudaUnregisterFatBinary(void** fatCubinHandle) {
    // TODO: Implement fat binary unregistration
    (void)fatCubinHandle;
}

void __cudaRegisterFunction(void** fatCubinHandle,
                           const char* hostFun,
                           char* deviceFun,
                           const char* deviceName,
                           int thread_limit,
                           uint3* tid,
                           uint3* bid,
                           dim3* bDim,
                           dim3* gDim,
                           int* wSize) {
    // TODO: Implement function registration
    // This function should:
    // 1. Map host function pointer to kernel name
    // 2. Store mapping for kernel launch
    (void)fatCubinHandle;
    (void)hostFun;
    (void)deviceFun;
    (void)deviceName;
    (void)thread_limit;
    (void)tid;
    (void)bid;
    (void)bDim;
    (void)gDim;
    (void)wSize;
}

void __cudaRegisterVar(void** fatCubinHandle,
                      char* hostVar,
                      char* deviceAddress,
                      const char* deviceName,
                      int ext,
                      size_t size,
                      int constant,
                      int global) {
    // TODO: Implement variable registration
    (void)fatCubinHandle;
    (void)hostVar;
    (void)deviceAddress;
    (void)deviceName;
    (void)ext;
    (void)size;
    (void)constant;
    (void)global;
}

void __cudaRegisterManagedVar(void** fatCubinHandle,
                              void** hostVarPtrAddress,
                              char* deviceAddress,
                              const char* deviceName,
                              int ext,
                              size_t size,
                              int constant,
                              int global) {
    // TODO: Implement managed variable registration
    (void)fatCubinHandle;
    (void)hostVarPtrAddress;
    (void)deviceAddress;
    (void)deviceName;
    (void)ext;
    (void)size;
    (void)constant;
    (void)global;
}

/**
 * @brief Stream management functions
 */

cudaError_t cudaStreamCreate(cudaStream_t* pStream) {
    // TODO: Implement stream creation
    (void)pStream;
    return cudaSuccess;
}

cudaError_t cudaStreamDestroy(cudaStream_t stream) {
    // TODO: Implement stream destruction
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaStreamSynchronize(cudaStream_t stream) {
    // TODO: Implement stream synchronization
    (void)stream;
    return cudaSuccess;
}

/**
 * @brief Event management functions
 */

cudaError_t cudaEventCreate(cudaEvent_t* event) {
    // TODO: Implement event creation
    (void)event;
    return cudaSuccess;
}

cudaError_t cudaEventDestroy(cudaEvent_t event) {
    // TODO: Implement event destruction
    (void)event;
    return cudaSuccess;
}

cudaError_t cudaEventRecord(cudaEvent_t event, cudaStream_t stream) {
    // TODO: Implement event recording
    (void)event;
    (void)stream;
    return cudaSuccess;
}

cudaError_t cudaEventSynchronize(cudaEvent_t event) {
    // TODO: Implement event synchronization
    (void)event;
    return cudaSuccess;
}

cudaError_t cudaEventElapsedTime(float* ms, cudaEvent_t start, cudaEvent_t end) {
    // TODO: Implement elapsed time calculation
    (void)ms;
    (void)start;
    (void)end;
    if (ms) {
        *ms = 0.0f;
    }
    return cudaSuccess;
}

#ifdef __cplusplus
}
#endif
